KR20180102680A - Method for producing dry powder - Google Patents

Abstract

CLAIMS What is claimed is: 1. A method for making a dry powder in a facility comprising a first drying chamber, which is a backmixing drying chamber comprising at least one heating element, and a second drying chamber, wherein a mixture of powder and diluent is introduced into the first drying chamber, The pre-dried powder is transferred from the first drying chamber into the second drying chamber, the dry powder is formed in the second drying chamber, and the recirculating portion of the dry powder is transferred from the second drying chamber into the first drying chamber And the discharge portion of the dry powder is discharged from the second drying chamber.

Description

Method for producing dry powder

This disclosure provides a method for making a dry powder from a mixture of a diluent and a powder.

Drying methods for powders are well known in the art. Tray drying has been used for a long time, but has been largely replaced by a fluidized bed drying method due to increased drying speed. The concept of fluid bed drying is known in the art and is used for the drying of wet solids. Fluid bed drying is controlled and provides uniform drying conditions.

However, fluidized bed drying is associated with problems. When a wet cake or slurry is introduced, it may not be readily fluidizable. Even if the consistency of the fluid is achieved, the wet cake is often not fully fluidized. However, in this case, a portion of the cake may block holes or openings in the grid, such as a perforated plate, to cause accumulation of wet material. In addition, the non-fluidized portion can cover the heating element, thereby significantly reducing the heating efficiency. If such clogging of the openings or interruption of the heating element occurs, the installation must be stopped and cleaned. In particular, if the powder to be dried contains a significant amount of low molecular weight polyolefin species, which typically have waxy consistency, fouling and ultimately heat blockage of the heating panel will occur, requiring deactivation and cleaning of the heating panel can do. The cleaning procedure described above can result in a downtime of a few days of the plant, causing production losses, increasing maintenance costs, and significantly reducing the throughput of such a facility.

It is known that recycling of the material can be used to fluidize the feed material which is not readily fluidizable. However, this may result in a decrease in throughput and still require cleaning procedures quite often.

Although fluid bed drying by recirculation is several orders of magnitude faster than tray drying, there is still a need for a fast drying method that requires a low cleaning cycle.

EP 0 525 748 discloses a process for removing hydrocarbons from a polymer slurry in a heated flash tank. A portion of the slurry is removed from the flash tank, heated to a temperature above the operating temperature of the flash tank, and recycled to the flash tank. This will allow the solvent to be removed more effectively. However, such high temperatures are not suitable for all polymers. In addition, such processes require higher levels of safety and pressure resistance, and cleaning is still often required.

WO 2015188267 A1 discloses a plug flow, fluidized bed reactor having one or more underflow weirs for separating the product zone and the feed zone and allowing internal recirculation of the material from the product zone to the feed zone, Is used in a dry application. WO 2009/134142 A1 discloses a method for fluidized bed spray granulation of liquid product in an apparatus divided into at least two zones, wherein a feed stream of seed particles and a feed stream of liquid product are mixed with at least one of the zones Lt; / RTI >

Thus, there is a need to provide a method that features a higher throughput than previous solutions. Also, cleaning of the facilities used will be less often required when the method is used. Another goal is to reduce costs and maintain a high level of safety.

The present disclosure provides a method for making a dry powder in a facility,

I) a first drying chamber having a first top end section, an opposing first bottom end section and at least one first chamber sidewall, wherein the first drying chamber comprises at least one first heating element, at least one first powder inlet, A first drying chamber, which is a backmixed drying chamber comprising a powder outlet, at least one first gas inlet and a first gas outlet,

Ii) a second drying chamber having a second upper end section, an opposing second lower end section and at least one second chamber sidewall, the second drying chamber having at least one second heating element, a second powder inlet, A second drying chamber comprising at least one second gas inlet and a second gas outlet,

Iii) a first powder passageway for conveying the powder from the first drying chamber into the second drying chamber, the second powder passageway being connected to the second powder inlet or provided through a first powder outlet identical to the second powder inlet, and

Iv) a conveyor device for conveying the powder from the second drying chamber into the first drying chamber and optionally a second powder passageway.

In the facility, a mixture of powder and diluent having a weight average first concentration of diluent is introduced into the first drying chamber through at least one first powder inlet, and the pre-dried The powder is transferred from the first drying chamber through the first powder passageway into the second drying chamber and the diluent is mostly or completely removed from the mixture of powder and diluent after passing through the first and second drying chambers, Wherein the first average concentration of the diluent is higher than the second average concentration of the diluent, the second average concentration of the diluent is higher than the third average concentration of the diluent, and the second average concentration of the diluent is greater than the third average concentration of the diluent, The recirculating portion of the powder is conveyed from the second drying chamber into the first drying chamber using a conveyor device and optionally a second powder passage, The outlet is discharged from the second drying chamber.

In some embodiments, the method further comprises:

a) introducing a mixture of powder and diluent into the first drying chamber through at least one first powder inlet,

b) heating the mixture of powder and diluent with one or more first heating elements at a first temperature in a first gas flow introduced through the at least one first gas inlet and exiting through the first gas outlet, ≪ / RTI >

c) transferring the pre-dried powder through a first powder passageway into a second drying chamber,

d) heating the pre-dried powder by one or more second heating elements at a second temperature in a second gas flow introduced through the at least one second gas inlet and discharged through the second gas outlet, Forming step,

e) transferring the recycled portion of the dry powder from the second drying chamber into the first drying chamber through the conveyor device and optionally the second powder passage, and discharging the discharge portion of the dry powder from the second drying chamber through the second powder outlet .

In some embodiments, the first average concentration of the diluent in the mixture of powder and diluent is higher than the second average concentration of the diluent in the pre-dried powder and the second average concentration of the diluent in the pre-dried powder is greater than the second average concentration of the diluent in the dry powder The first average concentration of the diluent in the mixture of powder and diluent is in the range of 15% to 50% by weight, and the third average concentration of diluent in the dry powder is less than 10% by weight .

In some embodiments, the powder is a polymer powder.

In some embodiments, the powder is a polyolefin powder.

In some embodiments, the mixture of powder and diluent is a mixture of polyethylene and a hydrocarbon diluent.

In some embodiments, the polyolefin is a bimodal or multimodal polyolefin.

In some embodiments, the first and second gas flows are selected / selected from a nitrogen gas flow or a hydrocarbon gas flow, or the diluent is recycled as well as the first and second gas flows.

In some embodiments, the temperature of the first and second heating elements is in the range of 60 占 폚 to 125 占 폚 and / or the first and second heating elements are heated using water or steam.

In some embodiments, the average binding residence time of the powder in the first and second drying chambers is less than 60 minutes and / or the average recycle portion of the powder corresponds to 5% to 60% of the average total powder throughput.

In some embodiments, the facility comprises a first grid as a first intermediate floor comprising or consisting of a refractory material, wherein the first powder outlet and the first gas outlet are arranged on the first grid, 1 gas inlet is arranged below the first grid in such a manner that the first grid separates the at least one first powder inlet and the first powder outlet from the at least one first gas inlet, Wherein the first gas is guided from the at least one first gas inlet through the first grid to the first gas outlet and / or the facility comprises a refractory material or is comprised of a refractory material The second powder outlet and the second gas outlet are arranged on the second grid and the one or more second gas inlets are arranged on the second grid Wherein the second grid is arranged below the second grid in such a manner that the second powder inlet and the second powder outlet are separated from the at least one second gas inlet, And the second gas is directed from the at least one second gas inlet through the second grid to the second gas outlet.

In some embodiments, the first chamber sidewall also comprises at least a portion of the second chamber sidewall or is arranged immediately adjacent to the second chamber sidewall, wherein the first chamber sidewall comprises a first powder passageway, Is the first opening in the first chamber sidewall.

In some embodiments, the conveyor is selected from the group consisting of a spiral conveyor, a tube chain conveyor, and a pneumatic conveying device.

In some embodiments, the at least one first and second heating elements are a tube bundle type or plate type and are arranged within the chamber at a predetermined distance from at least one of the first and second chamber walls, Element is thermally coupled to at least one first chamber side wall or is integrated into at least one first chamber side wall and one or more second heating elements are in thermal working connection with at least one second chamber side wall, Lt; RTI ID = 0.0 > sidewalls < / RTI >

The present disclosure further provides a method for making a polyolefin,

a) continuously polymerizing one or more olefin monomers in a diluent at a temperature of from 20 DEG C to 200 DEG C and a pressure of from 0.1 MPa to 20 MPa in the presence of a polymerization catalyst in one or more polymerization reactors,

b) producing a slurry comprising solid polyolefin particles and a diluent,

c) mechanically separating the polyolefin particles from a portion of the diluent to produce a mixture of a polyolefin powder and a diluent having a lower content of diluent than the slurry produced in step b)

d) drying the mixture of the polyolefin powder and the diluent obtained in step c) according to the embodiment of the method for producing dry powder.

Figure 1 shows a schematic view of a process for the preparation of the polymer powder before the drying step;
Figure 2 shows a first embodiment of a setup of a drying chamber for producing a dry powder according to the method of the present disclosure;
Figure 3 shows a schematic of the setup of Figure 2 in a facility suitable for the method according to the present disclosure;
Figure 4 shows a second embodiment of the setup of a drying chamber for producing a dry powder according to the method of the present disclosure; And

For the production of a dry powder, two chamber systems having a first drying step and a separate second drying step are known in the art. The entire system is designed to prevent mixing of powders from the first and second chambers. Thus, only small holes are typically used to transfer a limited amount of relatively wet powder from the first chamber to a second chamber containing relatively dry powder. The purpose of the two chamber systems is to prevent the mixing of powders, in particular to prevent the transfer of relatively dry powder from the second chamber to the first chamber. Surprisingly, however, recycling in accordance with the present disclosure is advantageous for two chamber systems and in particular for drying procedures, for example increasing the fluidity and fluidity of the mixture in the first drying chamber, reducing fouling, reducing downtime, In terms of reduction in number of times and duration, reduction in maintenance cost, and reduction in production loss. And, according to the method of the present disclosure, the throughput can be remarkably increased.

The use of "and / or" is broadly defined so that the terms "a and / or b" are to be read as including the set "a and b", "a or b", "a" . Preferably and in most cases, "a and / or b" is associated with two entities "a" and "b ", at least one of the entities being present in the described embodiment.

It is to be understood that the term powder relates to a plurality of solid particles which can flow in the dry state. However, this term is not necessarily associated with a particular consistency when the powder is mixed with a diluent. If a liquid is rarely used, this will have little effect on the properties of the powder. When many liquids are combined with the powder, a cake of a certain degree of solidity can be formed. If much more diluent is used, a slurry or suspension is formed. Preferably, the powder is associated with a particulate material having an average particle diameter of from 50 mu m to 3000 mu m.

It is to be understood that the term "dried" or "dry" refers to the thermally assisted removal of a diluent which may be any liquid such as a hydrocarbon liquid or water. Preferably, the liquid is a hydrocarbon liquid.

The drying chamber of the facility includes various inlets and outlets for supplying powder and gas to the drying chamber and for withdrawing from the drying chamber. Each of these inlets and outlets may be a single inlet or outlet. However, these inlets or outlets may also be configured as a plurality of inlets and outlets. It is meant that each of these inlets and outlets may be a combination of two, three, four or more of these inlets and outlets. In a preferred embodiment of the method of the present disclosure, the first powder inlet has two to eight first powder inlets, more preferably two to six first powder inlets, and in particular two to four first powder inlets .

The first powder passageway for transferring the powder from the first drying chamber into the second drying chamber is preferably an opening in the first wall of the first chamber or comprises this opening. If the first wall is also part of the second chamber or immediately adjacent to the second chamber, this opening can be identical to the second powder inlet, i. E. Associated with the same opening that functions as part of the powder passageway or powder passageway . However, in one embodiment according to the present disclosure, the powder passageway may be formed by a tube or pipe having two ends forming a first powder outlet and a second powder inlet. Moreover, the powder passageway may also be formed by an intermediate chamber connected to the first powder inlet and the second powder outlet.

In a preferred embodiment of the method according to the present disclosure, the method comprises the steps of:

a) a mixture of a powder and a diluent (the first mixture of powder and diluent) having a weight unit first average concentration of the diluent is introduced into the first drying chamber through one or more first powder inlets, for example 1 to 8 powder inlets, Lt; / RTI >

b) heating the mixture by at least one first heating element at a first temperature in a first gas flow introduced through the at least one first gas inlet and exiting through the first gas outlet, Forming a pre-dried powder (a second mixture of powder and diluent) having a concentration,

c) transferring the pre-dried powder through a first powder passageway into a second drying chamber,

d) heating the pre-dried powder by one or more second heating elements at a second temperature in a second gas flow introduced through the at least one second gas inlet and exiting through the second gas outlet, Forming a dry powder (third mixture of powder and diluent) having a unit third average concentration,

e) transferring a portion of the dry powder comprising the recycled portion of the dry powder from the second drying chamber through the conveyor apparatus and optionally the second powder passage into the first drying chamber, and discharging the dry powder from the second drying chamber And discharging through a second powder outlet.

It has been found that by dividing the dry powder into the recirculating portion and the outlet portion as described above, it is possible to improve the drying method in which the content of the residual diluent can be effectively reduced in combination with better operability. According to the method of the present disclosure, the separation of the diluent is typically accomplished by evaporation. The evaporated diluent exiting the first and second drying chambers by the aid of the gas flow can be captured by condensing means, for example a condensation column, and can also be separated from the gases of the first and second gas flows . In general, a mixture of powder and diluent (the first mixture of powder and diluent) prior to introduction into the first drying chamber is subject to prior mechanical separation of the diluent. In many cases, especially when the mixture contains polymer particles such as polyolefin particles, the diluent concentration of the resulting mixture after mechanical separation of the diluent ranges from 15% to 60% by weight.

In the method of the present disclosure, the first average concentration of the diluent is higher than the second average concentration of the diluent, and the second average concentration of the diluent is higher than the third average concentration of the diluent. The third average concentration of the diluent is preferably at least 75% lower, more preferably at least 90% lower than the first average concentration. In one preferred embodiment, the first average concentration of the diluent is in the range of 15 wt% to 50 wt%, the third average concentration of the diluent is less than 10 wt%, such as less than 1 wt%, or even less than 0.1 wt% Or less. In most cases, the residual diluent content in the dry powder of up to 1% by weight can be achieved by the method of the present disclosure. Recirculation of dry powder (a third mixture of powder and diluent) that is significantly dry than a mixture of introduced powder and diluent (the first mixture of powder and diluent) results in improved fluidization within the first chamber. The method of the present disclosure typically achieves a homogeneous distribution of the diluent in the powder present in the first chamber in a short period of time. That is, the residual diluent content in the particles in the first chamber is essentially the same for the entire contents of the first chamber.

Preferably, the amount of diluent evaporated in the first drying chamber is between 70% and 97% by weight of the amount of diluent evaporated in the drying facility, and the amount of diluent evaporated in the second drying chamber is preferably evaporated in the drying facility 3% to 30% by weight of the amount of diluent.

In a preferred embodiment, in step c) and / or e) the powder is continuously transported. This can be advantageous in providing continuous throughput.

Also in a preferred alternative embodiment, in step c) and / or e) the powder is intermittently transported. This is preferably done by an automatic method in which the powder is removed regularly, preferably after a certain time interval.

Generally, the first temperature is lower than the second temperature. Preferably, the first temperature is in the range of 50 占 폚 to 90 占 폚, more preferably 55 占 폚 to 70 占 폚, the second temperature is in the range of 60 占 폚 to 105 占 폚, and more preferably 75 占 폚 to 100 占 폚.

Preferably, the powder is a polymer powder. In particular, polyolefins have been found to be efficiently dried using the above process. In a particularly preferred embodiment, the mixture of powder and diluent is a mixture of polyethylene and a hydrocarbon diluent or a mixture of a polypropylene and a hydrocarbon diluent.

The methods of the present disclosure are particularly suitable for drying bimodal or multimodal polyolefms, wherein the term bimodal and multimodal refers to the modality of the polymer composition and thereby frequently refers to the modality of the molecular weight distribution. Such a polymer can be obtained by polymerizing the olefin in the cascade of two or more polymerization reactors under different reaction conditions. Thus, "modality" means how many different polymerization conditions are used to produce the polyolefin, independent of whether this modality of the molecular weight distribution can be perceived as the maximum value separated in the gel permeation chromatography (GPC) curve . Frequently used in the art, and as used herein, the term multimodal may include bimodal. It has been found that such bimodal or multimodal polyolefins typically require frequent cleaning of the facility and are particularly responsive to the procedures described, i.e. the cleaning frequency can be significantly reduced than expected.

Preferably, the temperature of the first and second heating elements is in the range of 60 캜 to 125 캜, particularly 80 캜 to 120 캜. Especially when the polyolefin in the hydrocarbon diluent is dried, higher temperatures have been found to adversely affect the efficiency of the heating element. Also, in one embodiment, the first and second heating elements are heated using water or steam. Suitable heating elements include plate type heating elements and tube bundle type heating elements.

In another preferred embodiment, the mean bond residence time of the powder in the first and second drying chambers is less than 60 minutes, in particular less than 30 minutes. The required average bond retention time is influenced by the temperature of the first and / or second heating element, the velocity of the first and / or second gas flow, the type of diluent and the amount of recirculation, among other effects.

It is also preferred that the average recycle portion of the powder is between 5% and 60%, especially between 10% and 50% of the average total powder throughput. Surprisingly, a somewhat greater amount of recycle makes the overall throughput good, but many dried materials are re-supplied to the drying process. The improved fluidity of the mixture of the first chambers is believed to greatly overcome the negative effects of increasing the drying efficiency and re-feeding the already dried material back into the drying process.

In some embodiments of the method, the facility comprises a first grid as a first intermediate floor comprising or consisting of a refractory material, wherein the first powder outlet and the first gas outlet are connected to a first grid And the at least one first gas inlet is arranged below the first grid in such a manner that the first grid separates the at least one first powder inlet and the first powder outlet from the at least one first gas inlet, The grid is the first intermediate floor in which the powder is fluidized thereon in the first chamber. The first grid may be, for example, a perforated plate or a sparger plate. In a preferred embodiment, more than one first powder inlet is used, for example from 2 to 6, or preferably from 2 to 4, first powder inlets. Preferably, the first gas is directed from the at least one first gas inlet to the first gas outlet through the first grid. In this embodiment, the powder is dried by a first gas flow that flows through the grid and escapes through the first gas outlet to continuously deliver the diluent. In one embodiment, the space under the first grid is divided into two or more, for example four, five or six, separate compartments through which the first gas from the at least one first gas inlet is passed through the first grid . In another embodiment, a plurality of first gas inlets are used below the grid, with at least one of the compartments described above.

In another embodiment of the method, the second chamber is characterized by a similar setup, the facility comprising a second grid as a second intermediate floor comprising or consisting of a refractory material, the second powder inlet, The second powder outlet and the second gas outlet are arranged on the second grid and the at least one second gas inlet is arranged in such a way that the second grid separates the second powder inlet and the second powder outlet from the at least one second gas inlet And the second grid is a second intermediate floor in which the powder is fluidized thereon in the second chamber and the second gas flow is directed from the at least one second gas inlet through the second grid to the second gas outlet, . The second grid may be, for example, a perforated plate or a sparger plate. In one embodiment, the space beneath the second grid comprises two or more, e.g., four, five, or six separate compartments, through which a second gas exiting the one or more second gas inlets is passed through the second grid .

It should be noted that the terms "upper", "upper" or "upper" as well as "lower", "lower" or "lower" refer to the arrangement of elements according to Earth's gravity in the assembly and use facility. Thus, the lower section is closer to the center of the earth than the upper section. This does not exclude unavailable steps beyond the array, for example, during the return to the installation site of the dismantled facility.

Preferably, both chambers have a grid as described above. In particular, it is preferred that the chambers have similar dimensions, wherein the volumes in each chamber, i.e., the available space, are different from one another to 75% or less, preferably 50% or less, especially 25% or less.

In one embodiment of the method, the first chamber side wall also constitutes at least a portion of the second chamber side wall or is arranged immediately adjacent to the second chamber side wall, the first chamber side wall including a first powder passageway, The first powder passageway is the first opening of the first chamber side wall. Thus, the distance over which the powder must be conveyed is minimized. The first chamber sidewall may include a second powder passageway extending from the upper portion of the first powder passageway and / or from the upper portion of the first chamber sidewall to the second drying chamber, It is an opening. However, it is also not possible to completely avoid some material from passing from the first chamber through the second powder passageway into the second chamber. This can limit the efficiency increase to some extent as described. Thus, using a conveyor device to transfer material from the second chamber into the first chamber may be controlled by controlling the flow rate of the powder transferred from the second drying chamber to the first drying chamber, for example, by adjusting the speed of the conveyor . This allows, for example, adapting the recirculation flow rate to the nature of the powder to be dried. In the case of products which are more difficult to fluidize, the flow rate can be increased, while in other cases the flow rate can be kept at the minimum value. It is also conceivable to use a combination of the second powder passageway and the conveyor device.

Preferably, the conveyor device is selected from the group consisting of a spiral conveyor, a tube chain conveyor and a pneumatic conveying device. The conveyor has been found to be advantageous when operating with powder. Helical conveyors, also called screw conveyors, are particularly preferred.

In another embodiment of the method, the at least one first and second heating elements are tube bundle type or plate type, and are arranged inside the chamber at a predetermined distance from at least one of the first and second chamber walls.

Additionally or alternatively, the at least one first heating element may be thermally coupled to the at least one first chamber side wall or integrated into / integrated with the at least one first chamber side wall, Or in at least one second chamber sidewall of the second chamber.

Preferably, the first gas flow is guided through the first chamber, the at least one first gas inlet introduces a first gas flow into the chamber, and the first gas outlet discharges the first gas flow from the first chamber . Additionally, the second gas flow may be guided through the second chamber, wherein the at least one second gas inlet introduces a second gas flow into the chamber, and the second gas outlet discharges the second gas flow from the second chamber .

In another embodiment of the method, the first gas outlet comprises a first gas outlet for separating the residual powder carried from the first chamber through the first gas outlet from the diluent and gas carried through the first gas outlet, 1 separation unit, preferably a first cyclone separator. The residual powder separated by the first separation unit is preferably introduced into the second chamber through the third powder inlet.

In another embodiment of the method of the present disclosure, the second gas outlet separates the residual powder carried from the second chamber through the second gas outlet by the second gas flow from the diluent and gas carried through the second gas outlet To a second separation unit, preferably a second cyclone separator. The residual powder separated from the second gas flow by the second separation unit is preferably added to the powder discharged through the second powder outlet.

The method may be practiced using first and second gas flows selected from a nitrogen gas flow or other inert gas flow or a hydrocarbon gas flow. It is particularly preferred that the diluent is recycled as well as the first and second gas flows. In particular, it is preferred that the first and second gas flows be part of a larger gas circulation path, wherein the first gas flow is directed to a third separation unit separating the gas from the diluent, in particular to a condensation column, To form a second gas flow through the second chamber from the second gas outlet to the at least one second gas inlet. In the circulation path, the second gas flow is directed to the at least one first gas inlet of the first chamber after passing through the second gas outlet and the second separation unit, wherein the first gas flow forms a first gas flow . In the condensation column, the diluent is liquefied and recovered so that it can be used again, for example, in the polymerization process.

Preferably, the third separation unit is a condensation column that is cooled by a cooling fluid. In one advantageous embodiment, the diluent is also a cooling fluid. Further, the third separation unit preferably includes a discharge unit for the diluent.

Preferably, the gas circulation path comprises at least one gas transfer device. In particular, it is preferred that the second gas flow comprises first and second gas transfer devices. In one embodiment, the first gas transfer device is arranged downstream of the third separation unit in the gas circulation path and upstream of the at least one second gas inlet, and the second gas transfer device is arranged in the gas circulation path, Downstream and upstream of at least one of the first gas inlets. Preferably, said gas transfer device is a fan or blower.

In one embodiment of the method, the gas and the powder are heated inside the first and second chambers. Due to the evaporation of the diluent in the chamber, the temperature of the gas flow after exiting the chamber may in some cases be lowered compared to the temperature of the gas introduced into the chamber. However, due to the heating element inside the chamber, the temperature of the gas flow may also be kept essentially constant or even raised.

According to some embodiments of the method of this disclosure, the recirculation and discharge portions of the dry powder may be separated before these portions are removed from the chamber using the second and third powder outlet, or both portions may be separated from the second chamber powder And then separated into recirculation and discharge portions. It is contemplated that other possibilities in accordance with the present disclosure may be provided, for example, that the second separation unit at least partially provides the recirculation portion.

The drying chamber may be constructed according to any known method for drying the particulate material. Thus, it is possible for the particles to freely flow through the entire internal space of the drying chamber. However, it is also possible for the drying chamber to include a facility for directing the flow of the particles, in part or in large part, in the drying chamber. The first drying chamber is a back-mixing drying chamber; Which means that the contents of the first drying chamber can freely flow through the entire interior space of the first drying chamber. The second drying chamber is preferably a backmix drying chamber or a plug-flow drying chamber, i.e. a drying chamber in which all the particles move through the drying chamber at the same rate.

In one embodiment of the method of the present disclosure, the facility includes one or more additional drying chambers between the first drying chamber and the second drying chamber. The pre-dried powder discharged from the first drying chamber is then passed through these one or more additional drying chambers, preferably further including a further reduction in the average concentration of the diluent, and finally the pre- Is introduced into the drying chamber. The one or more additional drying chambers are not necessarily provided with a heating element.

It is to be understood that the units, embodiments and other elements explicitly described as being suitable for a particular method are preferably used as part of such a method. Therefore, the first gas inlet is preferably used in a gas injection method, the heating element is preferably used in a method for a heating step, the gas transfer gas is preferably used in a gas transfer method, etc. have.

The present disclosure further provides a method of making a polyolefin,

a) continuously polymerizing one or more olefin monomers in a diluent at a temperature of from 20 DEG C to 200 DEG C and a pressure of from 0.1 MPa to 20 MPa in the presence of a polymerization catalyst in one or more polymerization reactors,

b) producing a slurry comprising solid polyolefin particles and a diluent,

c) mechanically separating the polyolefin particles from a portion of the diluent to produce a mixture of a polyolefin powder and a diluent having a lower content of diluent than the slurry produced in step b)

d) drying the mixture of the polyolefin powder and the diluent obtained in step c) by the method as described above.

Polyolefins obtained under the above reaction conditions and mechanically separated from the diluent according to step c) were found to be particularly well dried using this method.

The polyolefin may be, but is not limited to, homopolymers or copolymers of olefins and 1-olefins, i.e., hydrocarbons having terminal double bonds. Preferred monomers are non-polar olefinic compounds comprising aryl-substituted 1-olefins. Particularly preferred 1-olefins are linear or branched C ₂ -C ₁₂ -1-alkenes, especially linear C ₂ -C ₁₀ -1-alkenes such as ethylene, propylene, 1-butene, 1-pentene, Octene, 1-decene or branched C ₂ -C ₁₀ -1-alkene such as 4-methyl-1-pentene, conjugated and nonconjugated dienes such as 1,3-butadiene, Diene or 1,7-octadiene or a vinyl aromatic compound such as styrene or substituted styrene. It is also possible to polymerize mixtures of various 1-olefins. Suitable olefins also include those in which the double bond is part of a cyclic structure which may have one or more ring systems. Examples include cyclopentene, norbornene, tetracyclododecene or methyl-norbornene or dienes such as 5-ethylidene-2-norbornene, norbornadiene, ) Or ethylnorbornadiene. It is also possible to polymerize a mixture of two or more olefins.

The polymerization process is in particular a process for producing homopolymers or copolymers of ethylene or propylene. As the comonomer in the polymerization of propylene, 40 wt% or less of ethylene and / or 1-butene is preferably used.

In a preferred embodiment, the process of the present disclosure refers to producing a polyolefin obtained by homopolymerizing or copolymerizing ethylene. It is particularly preferred to prepare polyethylene which is copolymerized with up to 40% by weight of C ₃ -C ₈ -1-alkene, preferably 1-butene, 1-pentene, 1-hexene, 1-octene or mixtures thereof . Particular preference is given to a process in which ethylene is copolymerized with up to 20% by weight of 1-butene, 1-hexene or mixtures thereof.

The process of the present disclosure can be used to dry any type of conventional polyolefin. The polyolefin may be prepared by any industrially known low pressure polymerization process which is carried out in the presence of a diluent. This is carried out at a temperature in the range from 20 캜 to 200 캜, preferably from 30 캜 to 150 캜, particularly preferably in the range from 40 캜 to 130 캜, and under a pressure of from 0.1 MPa to 20 MPa, particularly preferably from 0.3 MPa to 5 MPa And a suspension or slurry process. The polymerization can be carried out batchwise or preferably continuously in one or more stages. Processes of this type are generally known to those skilled in the art. The polymerization of the present disclosure is preferably carried out in a slurry, particularly in a loop reactor or a stirred tank reactor. That is, it means that the polymerization takes place in a medium, a so-called suspension medium, which is in a liquid or supercritical state under the conditions in each polymerization reactor, wherein the polyolefin produced is insoluble and forms solid particles. The solids content of the slurry generally ranges from 10% to 60% by weight, preferably from 20% to 40% by weight.

Suspension media forming the liquid or supercritical phase of the slurry typically comprise diluent as the main component, but may contain, for example, dissolved monomers or comonomers, dissolved cocatalyst such as aluminum alkyl or scavenger, , Dissolved reaction adjuvants such as hydrogen, or other components such as dissolved reaction products of polymerization reactions such as oligomers or waxes. Suitable diluents should be inert, i. E. Should not be decomposed under the reaction conditions. Such diluents are, for example, hydrocarbons having 3 to 12 carbon atoms, in particular saturated hydrocarbons such as isobutane, butane, propane, isopentane, pentane, hexane or octane or mixtures thereof. It is also possible to use unsaturated hydrocarbons such as propylene itself as the diluent. The diluent preferably has a boiling point that is significantly different from the boiling point of these monomers and comonomers used to allow monomers and comonomers as starting materials to be recovered from the mixture by distillation. Such diluents are, for example, hydrocarbons having a boiling point of greater than 40 ° C or even greater than 60 ° C, or a high proportion of these hydrocarbons. Thus, the process of the present disclosure is characterized in that the polymerization comprises more than 50% by weight of saturated hydrocarbons having a boiling point of greater than 60 DEG C at 0.1 MPa or even more than 80% by weight of saturated hydrocarbons having a boiling point of greater than 60 DEG C at 0.1 MPa Lt; RTI ID = 0.0 > suspension medium. ≪ / RTI >

In a preferred embodiment of the present disclosure, the polymerization is carried out in a cascade of at least two polymerization reactors connected in series. Such a reactor is not limited to any particular design, but preferably the reactor is a loop reactor or a stirred tank reactor. The number of such cascade reactors is not limited, but preferably the cascade is comprised of two, three or four reactors, most preferably two or three reactors. When a cascade of polymerization reactors is used in the process of the present disclosure, the polymerization conditions in the polymerization reactor may differ depending on, for example, the nature and / or amount of the comonomer or the different concentrations of the polymerization aids such as hydrogen.

Another preferred slurry polymerization process is slurry polymerization in a loop reactor wherein the polymerization mixture is continuously pumped through a circulating reactor tube. As a result of the pumped circulation, continuous mixing of the reaction mixture is achieved, and the introduced catalyst and the supplied monomers are distributed in the reaction mixture. In addition, the pumped circulation prevents sedimentation of the suspended polymer. The removal of the heat of reaction through the reactor wall is also facilitated by the pumped circulation. Typically, these reactors consist essentially of a cooling jacket for removing reaction heat, and also a circulating reactor tube having at least one rising leg and at least one falling leg surrounded by a horizontal tube section connecting vertical legs. The impeller pump, the catalyst feeder and the monomer feeder, and also the exhaust facility, and thus the conventional settling leg, are typically installed in the lower tube section. However, the reactor can also have more than two vertical tube sections, resulting in a meandering arrangement.

Preferably, the slurry polymerization is an ethylene polymerization carried out in a loop reactor at an ethylene concentration of at least 5 mol%, preferably 10 mol%, based on the suspension medium. In this context, the suspending medium does not refer only to the suspended medium supplied, such as isobutane, but rather to a mixture of such supplied suspending medium and the monomers dissolved therein. The ethylene concentration can be readily determined by gas-chromatographic analysis of the suspending medium.

The polymerization can be carried out using all customary olefin polymerization catalysts. It is believed that the polymerization can be carried out using a chromium oxide based Phillips catalyst, a titanium based Ziegler or Ziegler-Natta catalyst, or a single-site catalyst . For the purposes of this disclosure, a single-site catalyst is a catalyst based on chemically homogeneous transition metal coordination compounds. Particularly suitable single-site catalysts are catalysts based on bulky sigma-bonded or pi-bonded organic ligands, such as mono-Cp complexes, typically metallocenes, Catalysts based on bis-Cp complexes referred to as catalysts, or catalysts based on late transition metal complexes, in particular iron-bisimine complexes. It is also possible to use a mixture of two or more of these catalysts for the polymerization of olefins. Such mixed catalysts are often referred to as hybrid catalysts. The use and preparation of these catalysts for olefin polymerization are generally known.

Preferred catalysts are preferably chigler types, including titanium or vanadium compounds, magnesium compounds, and optionally, particulate inorganic oxides as support materials.

The methods of the present disclosure are particularly suitable for drying bimodal or multimodal polyolefms, wherein the term bimodal and multimodal refers to the modality of the molecular weight distribution. Such a polymer can be obtained by polymerizing the olefin in the cascade of two or more polymerization reactors under different reaction conditions. However, it is also possible to obtain such a bimodal or multimodal polyolefin by using a mixed catalyst. In addition to the molecular weight distribution, the polyolefin may also have a comonomer distribution, and preferably the average comonomer content of the polymer chain having a higher molecular weight is higher than the average comonomer content of the polymer chain having a lower molecular weight.

The polyolefin is usually obtained as a powder which means in the form of small particles. Depending on the catalyst shape and size, and polymerization conditions, the particles typically have somewhat regular shape and size. Depending on the catalyst used, the particles of the polyolefin powder typically have an average diameter of several hundred to several thousand microns. In the case of chromium catalysts, the average particle diameter is typically from about 300 microns to about 1600 microns, and in the case of chisel type catalysts, the average particle diameter is typically from about 50 microns to about 3000 microns. Preferred polyolefin powders have an average particle diameter of 100 [mu] m to 250 [mu] m. The particle size distribution can advantageously be determined, for example, by sieving. Suitable techniques are, for example, vibratory sieve analysis or sieve analysis in an air jet.

A preferred polyolefin for preparing the polyolefin compositions of the present disclosure is polyethylene having an ethylene content of 50 wt% to 100 wt%, more preferably 80 wt% to 100 wt%, especially 98 wt% to 100 wt%. Accordingly, the content of other olefins in the polyethylene is preferably 0 wt% to 50 wt%, more preferably 0 wt% to 20 wt%, particularly 0 wt% to 2 wt%.

The preferred polyethylene composition obtained by the process of the present disclosure has a density of 0.90 g / cm3 to 0.97 g / cm3. Preferably, the density is in the range of 0.920 g / cm3 to 0.968 g / cm3, particularly 0.945 g / cm3 to 0.965 g / cm3. The density was measured by the method A (immersion) with a 2 mm thick compression molded plaque crystallized for 30 minutes in boiling water after being pressurized at 20 MPa for 8 minutes in DIN EN ISO 1183-1: 2004, 180 ° C It should be understood that the density is determined accordingly.

The method of the present disclosure may be used in the range of 0.5 g / 10 min to 300 g / 10 min, more preferably 1 g / 10 min to 100 g / 10 min, even more preferably 1.2 g / 10 min to 100 g / 10 min , in particular 1.5 g / 10 min to 50 g / 10 min, DIN EN ISO 1133: 2005, is particularly suitable for the production of polyethylene having a MFR under a load of 21.6kg _21.6, as determined by the condition G at a temperature of 190 ℃ .

According to the present disclosure, a semi-intuitive idea of implementing a recirculation system according to the present disclosure in two chamber systems, which is typically used to prevent any backmixing, results in a significant improvement in efficiency. In particular, it has been found that the polyolefin powder can be dried better than using the previous process.

Other features and advantages of the present disclosure will become apparent from the following description, which is set forth by way of example only and with no intention of restricting the invention with reference to the schematic drawings.

Figure 1 shows a preferred embodiment of a process for preparing polyolefins prior to application of the drying process according to the present disclosure. While the diluent for polymerizing the olefin in the slurry state in the first polymerization reactor 1 is fed to the reactor via the feed line 2, the other components of the reaction mixture, such as catalyst, monomers, possible comonomers and polymerization auxiliaries, Is supplied to the reactor through the above-mentioned supply line (3). As a result of the polymerization in the reactor (1), a slurry of solid polyolefin particles in the suspension medium is formed. This slurry is fed via line 4 to the second polymerization reactor 5 where further polymerization takes place. The new comonomer or additional components of the reaction mixture may be fed to the reactor 5 via one or more feed lines 6. Thereafter, the slurry of the reactor 5 is fed via line 7 to the third polymerization reactor 8 where further polymerization is carried out. One or more feed lines (9) make it possible to supplement the reactor (8) with comonomers or further components of the reaction mixture. The slurry of the solid polyolefin particles in the suspension medium formed in the reactor 8 is continuously conveyed through the line 10 to the regulating vessel 11 and the regulating vessel 11 is operated in such a manner that the average residence time is about 20 minutes . The contents of the conditioning vessel 11 are drawn by the pump 12 through line 13, through the heat exchanger 14 and into the collection vessel 15. On the one hand the cooling of the slurry in the regulating vessel 11 required to remove heat after polymerization occurring in the regulating vessel 11, on the other hand, since the hot slurry is continuously added through the line 10 and, on the other hand, A portion of the slurry cooled in the heat exchanger 14 is returned to the regulating vessel 11 via line 17 by evaporating a portion of the suspended medium and removing the gas produced through line 16, It is possible. Valves 18 and 19 are provided in lines 16 and 17 to regulate cooling, or to suppress either or both of them. The slurry is then passed through line 20 to a centrifuge 21 where the solid polyolefin particles are separated from the liquid suspending medium. The separated polyolefin particles still having residual water content of 10% to 40% by weight, i.e. residual diluent after mechanical removal of the liquid suspending medium, are guided to the dryer through line 22 and dried according to the method of the present disclosure. The separated suspended medium is conveyed via line 23 to a collection vessel 24 and from there to a polymerization reactor 1, 5 and / or 8 via a line 26 by a pump 25. The line 26 and its branch-off are provided with valves 27, 28 and 29.

Figure 2 shows a first embodiment of a setup of a drying chamber for producing a dry powder according to the method, the facility comprising a first upper end section 106, an opposed first lower end section 108, Wherein the first drying chamber 100 includes a first heating element 116, a first powder inlet 104, and a first powder passageway 114, A first gas inlet 110, and a first gas outlet 112 formed by a first gas outlet 112, Figure 2 further illustrates a second drying chamber 101 having a second upper end section 107, an opposing second lower end section 109, and a second chamber side wall that is identical to the first chamber side wall 122 at one side And the second drying chamber 101 is provided with a second heating element 117, a second powder inlet formed by a first powder passage which is an opening 114, a second powder outlet 124, a second gas inlet 111 ) And a second gas outlet (113). The first powder passageway, which is the opening 114 for transferring more powder from the first drying chamber into the second drying chamber than from the second drying chamber into the first drying chamber, has the same first powder outlet as the second powder inlet Lt; / RTI > According to this method, a mixture of powder and diluent is introduced into the first drying chamber 100 heated through the first powder inlet 104 and the pre-dried powder is heated through the first powder passageway 114 And is transferred into the second drying chamber 101. Most of the diluents include a first gas flow (not shown) that enters the first chamber through the first gas inlet 110 and exits the first chamber 100 through the first gas outlet 112, Using a second gas flow (not shown) that enters the second chamber 101 heated through the second gas inlet 111 and exits the second chamber through the second gas outlet 113, Is removed from the powder by evaporation in the second drying chamber (100, 101). The powder is dried on the first grid 118 in the first chamber 100 and on the second grid 119 in the second chamber 101. The gas flow penetrates each of the grids 118 and 119 and absorbs the vaporized diluent carried through the respective gas outlets 112 and 113 out of the chamber. A portion (300) of the obtained powder (126) is conveyed back into the first chamber (100) by the conveyor (302). The conveyor 302 conveys the powder to the first powder inlet 104. The powder exits the conveyor 302 through the outlet 304 and into the first chamber 100 along path 306. In the example of FIG. 2, path 306 is downward, and powder moves along the path due to gravity. It is also possible, however, to connect the conveyor 302 directly to the first chamber 100 in such a way that the powder falls directly into the first chamber 100 without the path 306, It is possible to dispose the second electrode 304.

Figure 3 shows a schematic of the setup of Figure 2 in a facility suitable for the method according to the present disclosure. For clarity, some reference numerals in Fig. 2 have been omitted from Fig. 3, but can be derived from Fig. The gas circulation fans 204 and 205 arranged outside the chambers 100 and 101 carry gas through the chambers 100 and 101, respectively. The gas exiting through the second gas outlet 113 is removed in the second cyclone separation step 203. The dry powder produced in the second cyclone separation step (203) may be combined with powder exiting through the second powder outlet (124). The gas generated in the second cyclone separation step 203 is conveyed by the fan 205 into the first chamber 100 through the first gas inlet 110. The gas exiting through the first gas outlet 112 is removed in the first cyclone separation step 202. The dry powder produced in the first cyclone separation step 203 may be introduced into the second chamber through a third powder inlet (not shown) in the upper section 107 of the second chamber 101. The gas exiting the second cyclone separating step 202 is conveyed to the condensation column 208 where the gas is separated from the diluent and is supplied to the second chamber 101 via the second gas inlet 111 by the fan 204 . The condensation tower 208 is cooled using a cooler 210. The diluent separated from the condensation column is pumped using the pump 212 in the circulation path. Thus, the diluent is used as a coolant and is simultaneously discharged through the diluent outlet 214 at the same time.

Figure 4 shows a second embodiment of the setup of a drying chamber for the production of a dry powder according to the process. Reference numerals are assigned according to FIG. Fig. 4 differs from Fig. 2 in that a second powder passageway formed by another opening 120 is provided to recycle the powder from the second drying chamber into the first drying chamber.

The features of the invention disclosed in the above description, the claims, and the drawings, both individually and in any combination, may be necessary to implement the invention in various embodiments.

Claims (15)

A method for making a dry powder in a facility,
The facility,
I) a first drying chamber having a first upper end section, an opposing first lower end section and at least one first chamber sidewall, the first drying chamber comprising at least one first heating element, at least one first powder inlet, 1 < / RTI > powder outlet, one or more first gas inlets and a first gas outlet,
Ii) a second drying chamber having a second upper end section, an opposing second lower end section and at least one second chamber sidewall, the second drying chamber comprising at least one second heating element, a second powder inlet, A second drying chamber comprising an outlet, at least one second gas inlet and a second gas outlet,
Iii) a first powder passageway for conveying the powder from the first drying chamber into the second drying chamber, the first powder passageway being connected to the second powder inlet or provided through the same first powder outlet as the second powder inlet, and
Iv) a conveyor device for conveying the powder from the second drying chamber into the first drying chamber and optionally a second powder passageway,
A mixture of powder and diluent having a weight average first unit concentration of diluent is introduced into the first drying chamber through the at least one first powder inlet and the pre-dried powder having a weight unit second average concentration of diluent Wherein the first drying chamber is connected to the second drying chamber through the first powder passageway,
Wherein the diluent is mostly or completely removed from the mixture of powder and diluent after passing through the first and second drying chambers to form a dry powder having a third weight average molecular weight of the diluent in the second drying chamber,
The first average concentration of the diluent is higher than the second average concentration of the diluent, the second average concentration of the diluent is higher than the third average concentration of the diluent,
Wherein the recycle portion of the dry powder is transferred from the second drying chamber into the first drying chamber using the conveyor device and optionally a second powder passageway,
Wherein the discharge portion of the dry powder is discharged from the second drying chamber. The method according to claim 1,
a) introducing a mixture of powder and diluent into the first drying chamber through the at least one first powder inlet,
b) heating the mixture of powder and diluent with the at least one first heating element at a first temperature in a first gas flow introduced through the at least one first gas inlet and exiting through the first gas outlet, Forming said pre-dried powder,
c) transferring the pre-dried powder through the first powder passageway into the second drying chamber,
d) heating said pre-dried powder by said at least one second heating element at a second temperature in a second gas flow introduced through said at least one second gas inlet and through said second gas outlet , Forming the dried powder,
e) transferring the recycled portion of the dry powder from the second drying chamber into the first drying chamber through the conveyor device and optionally a second powder passage, and discharging the dry powder from the second drying chamber to the second drying chamber, 2 < / RTI > powder outlet. 3. The method of claim 2,
The first average concentration of the diluent in the mixture of powder and diluent is higher than the second average concentration of the diluent in the pre-dried powder and the second average concentration of the diluent in the pre- 3 < / RTI > average concentration and /
Wherein the first average concentration of the diluent in the mixture of powder and diluent is in the range of 15 wt% to 50 wt% and the third average concentration of diluent in the dry powder is less than 10 wt%. 4. The method according to any one of claims 1 to 3,
Wherein the powder is a polymer powder. 5. The method of claim 4,
Wherein the powder is a polyolefin powder. 6. The method of claim 5,
Wherein the mixture of powder and diluent is a mixture of polyethylene and a hydrocarbon diluent. The method according to claim 6,
Wherein said polyolefin is a bimodal or multimodal polyolefin. 8. The method according to any one of claims 2 to 7,
The first and second gas flows are selected and / or selected from a nitrogen gas flow or a hydrocarbon gas flow,
Wherein the first and second gas flows as well as the diluent are recycled. 9. The method according to any one of claims 1 to 8,
Wherein the temperature of the first and second heating elements is in the range of 60 캜 to 125 캜 and /
Wherein the first and second heating elements are heated using water or steam. 10. The method according to any one of claims 2 to 9,
The average bond residence time of the powders in the first and second drying chambers is less than / less than 60 minutes,
Wherein the average recycle portion of the powder corresponds to 5% to 60% of the average total powder throughput. 11. The method according to any one of claims 1 to 10,
Wherein the facility comprises a first grid as a first intermediate floor comprising or consisting of a refractory material and wherein the first powder outlet and the first gas outlet are arranged on the first grid, 1 gas inlet is arranged below the first grid in such a manner that the first grid separates the at least one first powder inlet and the first powder outlet from the at least one first gas inlet, Is a first intermediate floor in which powder is deposited thereon in the first chamber and a first gas is directed from the at least one first gas inlet through the first grid to the first gas outlet and /
Wherein the facility comprises a second grid as a second intermediate floor comprising or consisting of a refractory material and the second powder outlet and the second gas outlet are arranged on the second grid, 2 gas inlet is arranged below said second grid in such a manner that said second grid separates said second powder inlet and said second powder outlet from said at least one second gas inlet, Is a second intermediate floor that is deposited thereon in the second chamber and a second gas is guided from the at least one second gas inlet to the second gas outlet through the second grid. 12. The method according to any one of claims 1 to 11,
Wherein the first chamber sidewall further comprises at least a portion of the second chamber sidewall or is arranged immediately adjacent to the second chamber sidewall, the first chamber sidewall including the first powder passageway, Wherein the first chamber side wall is a first opening of the first chamber side wall. 13. The method according to any one of claims 1 to 12,
Wherein the conveyor is selected from the group consisting of a spiral conveyor, a tube chain conveyor and a pneumatic conveying device. 14. The method according to any one of claims 1 to 13,
Wherein the at least one first and second heating elements are tube bundle type or plate type and are arranged within the chamber at a predetermined distance from at least one of the first and second chamber walls,
Wherein the at least one first heating element is in thermally operational connection with the at least one first chamber side wall or is integrated into the at least one first chamber side wall and the at least one second heating element is in thermal contact with the at least one second chamber side wall, Wherein the at least one second chamber is thermally coupled to the sidewall or integrated into the at least one second chamber sidewall. As a method for producing a polyolefin,
a) continuously polymerizing one or more olefin monomers in a diluent at a temperature of from 20 DEG C to 200 DEG C and a pressure of from 0.1 MPa to 20 MPa in the presence of a polymerization catalyst in one or more polymerization reactors,
b) producing a slurry comprising solid polyolefin particles and a diluent,
c) mechanically separating the polyolefin particles from a portion of the diluent to produce a mixture of a polyolefin powder and a diluent having a lower content of diluent than the slurry produced in step b)
d) drying the mixture of the polyolefin powder and the diluent obtained in step c) by the process according to any one of claims 1 to 14.

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